Looks like the blue is just scotch-locked(spliced) into your current phone system then the tech would put an rj11 end on the blue pair and plug into the voip port of the rg and the green pair into the vdsl port.

If you have pots there would be no need to do anything else at the rg with the blue pair, just the green pair, as the blue would be already connected at the demarc and pass thru that filter.